We economists have a pretty strong consensus on a few key points: 1) innovation is the main cause of long-term economic growth, 2) social institutions are a key changeable determinant of social outcomes, and 3) inducing the collection and aggregation of info is one of the key functions of social institutions. In addition, better institutional-methods for collecting and aggregating info (ICAI) could help with the key meta-problems of making all other important choices, including the choice of our other institutions, especially institutions to promote innovation. Together all these points suggest that one of the best ways that we today could help the future is to innovate better ICAI.
Machine intelligence ought to be good at "collecting and aggregating info". Machines can act as participants in markets as well, of course, but let's not forget that we can upgrade the brains of our traders.
I would think you could persuade someone to donate/grant/give you specifically at least $1M.
Maybe one way to start would be to build a new organization (e.g. 'for-profit' firm or regular U.S. corporation) with basically no particular structure or purpose other than to test an (internal) prediction market. After typing that out, it still seems too vague, but my intuition is that somehow you'd want to avoid 'managers' with (reasonable) reasons to NOT want to be subject to the 'cruel' criticism of prediction markets.
I would think you'd also have some good candidate ideas for suitable organizations. Maybe an investment firm? Or something else that could be potentially organized around an internal prediction market from the beginning?
Not all spending is spending money.
"nor can these experiments be enabled merely with money" and "most socially valuable way to spend" seem in conflict.
Do you have any links describing in more detail the "dozens of efforts to use prediction markets to advise decisions inside ordinary firms" where "users are satisfied"?
Surprised you didn't link to this:
Note the "<". An intuitive rough estimate.
How did you come up with the ~$1M quote?